UNIT- III
Database Design and the E-R Model : Overview of the Design Process, The
Entity Relationship Model, Constraints, Removing Redundant Attributes in
Entity Sets, Entity Relationship Diagrams, Reduction to Relational
Schemas, Entity-Relationship Design Issues. Relational Database Design:
Features of Good Relational Designs, Atomic Domains and First Normal
Form, Decomposition Using Functional Dependencies, Functional-
Dependency Theory, Algorithms for Decomposition, Decomposition Using
Multivalued Dependencies, More Normal Forms.
UNIT – III / 2
DBMS NOTES (R21) PBR VITS – CSE / AI / IOT
Database Design and the E-R Model
3.1 Overview of the Design Process
Design of the Database Schema, design of the programs that access and update the data, design
of a security scheme for controlling access to the data are all involved in the creation of a
Database. The central role in the designing process involves the requirements of the user. For
designing a database, there are four phases, namely:
Initial Phase : The Initial Phase of database design is to fully describe the data needs of the
potential database users The database designer needs to interact extensively with domain experts
and users to carry out this task. The outcome of this phase is a specification of user requirements.
Conceptual Design Phase : The designer chooses a data model, by applying the concepts of the
data model that is chosen and translates these requirements into a conceptual schema of the
database. The entity-relationship model is typically used to represent the conceptual design.
The conceptual schema specifies the entities that are represented in the database, the attributes of
the entities, the relationships among the entities, and constraints on the entities and relationships.
Typically, the conceptual-design phase results in the creation of an entity-relationship diagram
that provides a graphic representation of the schema.
A fully developed conceptual schema also indicates the functional requirements of the enterprise.
In a specification of functional requirements, users describe the kinds of operations (or
transactions) that will be performed on the data. The operations can include updating,